Electromotor-driven dental care devices are well known in the art. This includes tooth brushes where the brush head is driven oscillatingly about a rotational axis. The care head is located at the free end of a shank of the dental care device with its other end being a handle portion. In the handle portion an electric motor is disposed with a driving shaft in the shank.
Such a dental care device is described in DE 34 12 601 C2. The driving shaft of the dental care device carries at the care head end a driving pivot disposed eccentrically with respect to the driving shaft. The longitudinal axis of the driving pivot is inclined relative to the rotational axis of the driving shaft. For the conversion of the rotational turning movement of the driving shaft into an oscillatory movement of the care head an axial gap is introduced into a driving shaft of the care head and is disposed at right angles to the driving shaft supported in the shank. The driving pivot is disposed at an inclination so its longitudinal axis penetrates the axial gap. The driving shaft of the care head, in turn, is supported in multiple places in the shank.
A turning movement of the driving shaft and the driving pivot results in an oscillatory turning movement of this driving shaft through the engagement of the driving pivot into the axial gap of the rotationally supported driving shaft of the care head. In order to make possible such a movement the length of the axial gap must be greater than the diameter of the circular movement executed by the driving pivot within the axial gap. In order for the care head to function faultlessly, the rotational axes of the driving shaft supported in the shank and the driving shaft of the care head and the longitudinal axis of the driving pivot must virtually intersect in one point. Moreover, the two rotational axes must be disposed at right angles with respect to one another. The slightest deviations from this geometry can lead to an increased wear of the elements involved in the force conversion or to a canting misalignment of the driving pivot in the axial gap. In order to reduce as much as possible the play between the driving element, the bearing of the driving shaft of the care head and of the bearing of the driving shaft in the shank must be manufactured with very high tolerances. The outer bearing site of the driving shaft disposed in the shank must also be in closest possible proximity to the driving pivot. Moreover, dimensional and tolerance accuracy of the housing and bearing parts produced must be high. This is often hard in parts produced in an injection molding process.
The present invention discloses a dental care device without the disadvantages demonstrated regarding prior art devices. The present invention has a force converter which comprises a gymbal supported conversion element in which the driving element which engages the conversion element is fully supported. The rotational axes of the two gymbal bearings of the conversion element are disposed such that they form a right angle and intersect virtually in one point. The conversion element is swivellably supported by a mounting in which the conversion element is centered about one of the two rotational axes of the gymbal bearing; and the mounting is supported turnably about the other rotational axis of the gymbal bearing and carries the care head.